Bridges, part of transportation infrastructure, play a noticeable role in social and economic development. Taking the United States for example, there are more than 600,000 in-service bridges nationwide; an average age of these bridges is more than 40 years, and the deterioration of bridges account for about 25% of these bridges. The I-35W bridge in Minneapolis collapsed in the year 2007 and caused an economic loss of $200 million. At present, China is gradually emerging from the golden period of infrastructure construction. For more than 750,000 in-service bridges, a considerable part of which are facing aging problems. Research shows that the number of dangerous bridges of category four and five in China exceeds 90,000. In order to ensure the normal development of economy and society, it is urgently needed to maintain and manage these in-service bridges, practically and effectively. Vehicle load, which is the main form of loads in the service of the bridges, plays an important role in the degradation process of structural performance. Moreover, the safety threat to the bridge deck pavement and the bridge structure from the overload vehicles is becoming increasingly evident. In order to provide a valuable reference for better bridge maintenance management and engineering design, the problem of vehicle-bridge coupling has become a major research topic in the field of bridge engineering.
Due to the limit of conditions, it has been difficult to measure the actual dynamic vehicle load. Usually, the static mass of the vehicle is considered, while the gained vertical wheel impact force is ignored. As a result, the evaluation of bridge health conditions such as structural identification and the like is adversely affected. If complex algorithms considering parameters such as pavement roughness and the like are adopted, not only accurate pavement surface information needs to be provided, but also the calculation difficulty will be increased. Once the accurate wheel force of the vehicle during driving on the bridge rather than the static mass of the vehicle is obtained, the accuracy of the result recognition can be improved while the calculation difficulty is reduced, thereby significantly improving the evaluation effect of the health condition of the bridges.
At present, there are some methods and techniques for measuring wheel force, but they still have various drawbacks. The dynamic weighing system is a mature technique for detecting the overload vehicles in the highway network. However, the dynamic weighing system can only acquire the wheel force in a narrow range and a short time. For example, the dynamic weighing system can only acquire the wheel force at the time when the vehicle is passing the bridgehead, while it cannot acquire the wheel force of the vehicle during passing over the whole bridge. Wheel six-component force measuring system based on wheel hub strain can acquire force information of the wheels in three directions. However, strictly speaking, these six-component forces are specific to the hub deformation, which is different from the actual contact force between the tire and the ground. Therefore, using this technique in the evaluation of bridge health condition will inevitably cause errors. In addition, since such system has complicated construction, provides too much information and is costly, it has not been widely used in the field of bridge engineering.